Ceramic dielectric material comprising barium-sodium-niodium titanate

ABSTRACT

A CERAMIC MATERIAL IN A PEROVSKITE STRUCTURE HAVING A HIGH DIELECTRIC PERMITTIVITY A LOW POWER FACTOR AND A LOW TEMPERATURE COEFFICIENT TO PERMITTIVITY THE COMPOSITION OF WHICH IS IN A CHEMICAL FORMULA OF   BA(NA0.25XNB0.75TI1-X)O3   WHEREIN X RAGES FROM 0.01 TO 0.30 IN ACCORDANCE WITH THE INVENTIONS. THE CERAMIC DIELECTRIC COMPOSITION OF   BA(NA0.25XNHB0.75XTI1-X)O3   CAN BE MODIFIED BY SUBSTITUTIONO SR FOR BA OR LI FOR NA IN ACCORDANCE WITH THE INVENTIONS.

973 YOSHIHIRO MATSUO ET L 3 9- CERAMIC DIELECTRIC MATERIAL CQMPRISINGBARIUM'SQDIUM'NIODIUM TITANATE Filed June 12, 1970 YOSHIHIRO MATSUO,HIROMU SASAKI and H SHIGERU HAYAKAWA, Inventors Attorneys United StatesPatent 3,709,704 CEC DIELECTRIC MATERIAL COMPRESINGBARIUM-SODIUM-NIODIUM TITANATE Yoshihiro Matsuo, Hiromu Sasaki, andShigeru Hayalrawa, Osaka, Japan, assignors to Matsushita ElectricIndustrial Co., Ltd., Kadoma, Osaka, Japan Filed June 12, 1970, Ser. No.45,870 Claims priority, application Japan, July 29, 1969, 44/ 61,125;Oct. 13, 1960, 44/ 81,983, 44/ 81,984 Int. Cl. C041 33/00 I LS. Cl.106-459 R 3 Claims ABSTRACT OF THE DISCLOSURE A ceramic material in aperovskite structure having a high dielectric permittivity, a low powerfactor and a low temperature coefiicient of permittivity, thecomposition of which is in a chemical formula of wherein x ranges from0.01 to 0.30 in accordance with the inventions. The ceramic dielectriccomposition of can be modified by substitution of Sr for Ba or Li for Nain accordance with the inventions.

This invention relates to ceramic dielectric materials and morespecially to ceramic dielectric materials in a perovskite structure,which have a high dielectric permittivity, a low power factor and a lowtemperature coefficient of permittivity.

Since the recent electronic industry has required miniaturization andrefinement of electrical equipment, there is an increasing need for adielectric material of a high permittivity, a low power factor and a lowtemperature coeflicient of permittivity. High permittivity facilitatesproducing a capacitor in a small physical size for a given capacitanceand low power factor prevents a capacitor from being heated. Heatgeneration is a serious problem in miniaturized electrical equipment.Low temperature coeflicient of permittivity of a capacitor enableselectrical equipment or device to work in a high accuracy. It is alsodesired that the temperature coefficient of permittivity can be chosenat a specific value.

Therefore, it is an object of the present invention to provide ceramicdielectric materials characterized by high permittivity and low powerfactor.

Another object of the present invention is to provide ceramic dielectricmaterials characterized by high permittivity, low power factor and alinear temperature coefiicient of permittivity.

These and other objects will be apparent upon consideration of followingdetailed description taken together with accompanying drawing wherein:

The drawing illustrates a cross sectional view of capacitor contemplatedby the present invention.

Before proceeding with a detailed description of the nature of acapacitor embodying the invention, the construction of such a capacitorWill be described with reference to the drawing. In this drawing,character indicates generally a capacitor comprising a sintered disc 11of dielectric material according to the invention. The sintered disc 11is provided on two opposite surfaces with electrodes 12 and 13.-Theelectrodes 12 and 13 may be applied to the surface by any suitable andavailable method, for example, by firing-on silver electrode paintcommerically available. The disc 11 is a plate which may have "ice anyof suitable shapes, for example, circular, square or rectangular. Wireleads 15 and 16 are attached conductively to the electrodes 12. and 13,respectively by a connection means 14 such as solder or the like.

The sintered disc comprises a perovskite-type compound represented bychemical Formula 1;

t).25x 0.'75x 1x) 3 wherein x ranges from 0.01 to 0.30 in accordancewith the inventions. A sintered disc having a composition of chemicalFormula 1 is in a perovskite structure and has a permittivity of 220 to2000, a power factor lower than 10 10'- and a temperature coefiicient ofpermitivity of 350 to +800 p.p.m./ C. If the x in chemical Formula 1 isout of the range of 0.01 to 0.30, the resultant disc does not show apower factor less than 10x10- as shown in Table 1.

The ceramic dielectric composition of chemical Formula 1 can be modifiedby partial substitution of Sr for Ba in accordance with the invention:The Sr-modified composition is in a chemical Formula 2;

( r-x x) 0.25x 0.x 1x) s wherein x ranges from 0.01 to 0.30 inaccordance with the invention. A sintered disc having a composition ofchemical Formula 2 is in a perovskite structure and has a permittivityof 250 to 2400, a power factor lower than 10x10 and a temperaturecoefficient of permititivity of 330 to +1000 p.p.m./ C. If the x in thechemical Formula 2 is outside of the range of 0.01 to 0.30, theresultant disc does not show a power factor less than 10 10- as shown inTable 2.

The ceramic dielectric composition of chemical Formula 2 can be modifiedby substitution of Li for Na in accordance with the invention: TheLi-modified composition is represented by chemical Formula 3;

( l-x x) D.25x 0.'l5x 1x) 3 wherein x ranges from 0.01 to 0.30 inaccordance with the invention. A sintered disc having the composition ofchemical Formula 3 is in a perovskite structure and has a permittivityof 700 to 2200, a power factor lower than 10x10" and a temperaturecoefiicient of permitivity of 350 to +300 p .p.m./ C. If the x inchemical Formulae 3 is outside of the range of 0.01 to 0.30, theresultant disc does not show a power factor less than 10 1O- as shown inTable 3.

The compositions in chemical Formulae 1 to 3 can be prepared by mixturesof ingredient oxide in mole ratio dependent upon the chemical formulae.For example, the composition in chemical Formula I can be prepared bythe following mixture listed in Table 4, wherein x ranges from 0.01 to0.30. It is possible to employ, as the starting material, any compoundwhich is converted into an oxide during firing process. Operablestarting materials which may be employed in place of an oxide are, forexample, carbonates hydro-oxides, and oxalates. A given mixture is wellmixed in a wet ball mill, dried, calcinated, pulverized, and pressedinto discs. The pressed discs are fired at a given hydro-oxides, andoxalates. A given mixture is well mixed in a wet ball mill, dried,calcinated, pulverized, and pressed into discs. The pressed discs arefired at a given temperature dependent upon compositions of mixtures.The Ag-electrode is attached to the both surfaces of the fired disc.Permittivity and power factor of the disc are measured at a constantapplied field of 1 mHz as a function of temperature from to 300 C. Thetemperature coefficient of permittivity ((01)) is usually defined byperature as shown at the column 3 of the tables (final the followingequation: firing temperature). The permittivity and power factor 5 o at20 C. and 1 mHz are set forth at column 4 and E( )/E( c )X(80 c) column5 of Table 5, respectively. The temperature c0- wherem 5 efficients ofpermittivity are set forth in column 6 of e(80 C.) is a permittivity at80 C. Table 5. All the samples shown in the tables are desire( C.) is apermittivity at 20 C. able for use in a capacitor.

TABLE 1 Power First Final Pormit- (actor Temperature firing firingtivity at 20 C. coetlicicnt of Sample temperatemperaat 20 C. and 1111112 permittivity Number Composition ture C.) ture C.) and 1 mHz (Xl0-(p.p.m./ O.)

41 BaTiO: 1, 200 1,400 2, 800 100 3, 000 42. MNaomnzs bt).00'l75 0.W5) 3200 400 500 50 700 49 Ba(Nau.rzsNbusnTlmQOa 1,300 1, 500 160 13 -2l0TABLE 2 Power First Final Permitfactor Temperature firing firing tivityat 20 C. coeflieient of Sample temperatemperaat 20 C. and 1 mHzpermittivity Number Composition ture C.) ture C.) and 1 mHz (X10(p.p.m./ C.)

51 (13300305310005) (NaonmaNbq.00s1s i0.m)Oa 1, 250 1, 2, 000 -1, 000 5930.5 1'U.6)( 80.125 b0J'I5 10.5) 3 1,300 1,600 100 16 200 TABLE 3 PowerFirst Final Permitfactor Temperature firing firing tivity at 20 C.coeflicient of Sample temperatemperaat 20 O. and l mHz permittivityNumber Composition ture C.) ture G.) and 1 mHz (X10 (p.p.m./ C

61 (Baomssmooa)(Lin.uoiztNbqmoau ioms)O: 1, 1,430 2, 400 35 1, 500 69(Bao.aSr0.5)(Li0.i25Nb0.a1s 10.a)0a 80 1, 480 200 17 -250 EXAMPLE TABLE4 Ingredient: Mole ratio Compositions corresponding to the chemicalformulae Barium oxide (BaO) 1.00 listed in column 1 of Table 5 areprepared by using start- Sodium oxide (Na O) 0.125x ing materials ofbarium carbonate, strontium carbonate, 45 Niobium oxide (M1 0 0.375xsodium carbonate, lithium carbonate, titanium oxide, and Titanium oxide(T102) 1-x TABLE 5 Col. 1 Col. 2 Col. 3 Col. 4 Col. 5 Col. 6

43 Ba(Na0.o02sN o.0o1s'1io.na)Oa 1,250 1,450 2,000 10 +800 44Ba(Nao.oosNbo.oiaTlo.ns)0s 1, 250 1,470 1, 400 8 +200 45Ba(Nan.nusNbo.oa1sTio.os)Oa 1,250 1,470 1,800 6 -100 46Ba(Na0.u2sNbo.o7s i0.o)0a 1,300 1,480 550 4 -350 47B8(Na0.0sNbo.1tTi0.a)O3 1,300 1,480 300 5 320 48Ba(Nao.o1sNbo.2zsTiu.7)0a 1,300 1,500 220 7 200 52 (Bamn rom)(aonozsNbonmsTiumo)O3 1,250 1,450 2,400 10 +1, 000 3-" art-05002)(Nan.0os b0.0i5 10 .ns)Os 1,250 1,470 1,100 7 54. 8001 003)(ao.oo1sNb0.o22a 0.n1) s 1,250 1,470 900 6 55- amasmos)( aomzn bomuoms)0s 1,250 1,470 700 5 0 56- (BaosSrM) (NamzsTlofiOs 1,300 1,480 500 4--120 67. aus m)(NamNbmTimol 1,300 1,480 350 4 330 68- n-7 111.5)(80.07aNb0.22a iu.7)0s 1,300 1, 500 250 5 -240 62. 8010 1001) lonuzabonmsTiom) 250 1,440 200 10 0 63- aums rom) (L10.0fl5 0-015 0;9B) 250460 800 9 64- an-87 111.03)( D.0D75 b0.0225' 0.97) 3 1, 250 1, 460 1,400 7 +20 65. 8035 005)(L 0.0125Nb0.315T10.05)O3 1, 250 1, 460 1, 000 540 66. all-0 0.1) (L10 .02tNbo.o1sTio.o)Oa 1, 280 1, 470 $00 5 -100 67-(Bau oa)(LipmNboJsTiomOa 1, 280 1, 470 760 6 360 68." (Bao.1 ru.a)0.076Nb0.226T10.7)O3 1, 280 1,480 700 9 300 niobium oxide. The mixturesof starting materials in given 70 The embodiments of the invention inwhich exclusive compositions are intimately mixed in awet ball mill,dried, property or privilege is claimed are defined as follows: calcinedfor two hours at a temperature as shown at the 1. A sintered dielectricmaterial consisting essentially column 2 of the tables (first firingtemperature), pulverof a perovskite-type compound of the chemicalformula ized, and pressed at a pressure of 700 kg. per cm? into Ba(NaNb,, Ti )O wherein x ranges from 0.01

discs. The pressed discs are fired for two hours at a temto 0.30.

2. A sintered ceramic dielectric material consisting essentially of aperovskite type compound of the chemical formula (Ba Sr (Na Nb Ti )'O,wherein x ranges from 0.01 to 0.30.

3. A sintered ceramic dielectric material consisting essentially of aperovskite-type compound of the chemical formula (Ba ,,Sr )(Li Nb Ti )Owherein x ranges from 0.01 to 0.30.

References Cited UNITED STATES PATENTS 2,742,370 4/1956 Wainer 106-39 R2,452,532 10/1948 Wainer 10639 R 6 3,502,598 3/1970 Nitta et al. 252-6293,474,043 10/ 1969 Andersen et a1 252-520 3,231,799 1/ 1966 Prokopowiczet a1. 106-39 R OTHER REFERENCES Evans, R. C.: An Introduction toCrystal Chemistry, Cambridge, 1964, pp. 168-170.

JAMES E. POER, Primary Examiner w. R. SATTERFIELD, Assistant ExaminerUS. Cl. X.R.

